I will try and offer some help here. Finding the oem pulley for that might be tough.
1. You may be able to take that to a machine shop and have them turn it down a little with new grooves. It will make the pulley a little smaller, my maybe a quarter inch but if you have a way to take up some slack in the belt it is a viable solution.
2. The flywheel bolt pattern is the same from a12-a15 Other manufactures such as
prochem have pulleys that bolt on in a similar fashion. I have a pulley, (not for sale) of a prochem a12 that is very similar to yours. It has two extra pulley grooves to drive a pump and a air pump. They may not be in the way of anything on your machine and could be an option. If you measure your pulley outside diameter I will measure mine from the prochem and see if it is the same or close. John olsen has lots of prochem parts and may have one for sale.